Project Summary Clonal hematopoiesis (CH) arises from somatic mutations that impart a growth advantage in hematopoietic stem cells. While increasing the risk of hematological malignancy, unexpectedly CH also increases the risk of myocardial infarction and stroke. CH increases in frequency from age 40 onward and is present in >10% of people above the age of 70 identifying CH as a major non-traditional risk factor for atherosclerotic cardiovascular disease (CVD). Amongst the four common genetic variants associated with CH, the JAK2v617f (JAK2vf) mutation that increases JAK/STAT signaling imparts a 12-fold increased hazard ratio for coronary heart disease. These recent observations emphasize the absolute imperative to develop a precision medicine strategy to treat CVD in these patients. We have reported that mice harboring Jak2vf mutations in bone marrow cells exhibit increased atherosclerosis and inflammasome activation. Preliminary studies in mice have further revealed that within atherosclerotic lesions Jak2vf macrophages (M?) have increased IL-1 mediated proliferation. To model CH we utilized a mixed bone marrow transplantation model where 20% of bone marrow cells harbor Jak2vf mutations, and the remaining 80% are wild-type. In these Jak2vf-CH mice Jak2vf was present in ~25% of CD45+ blood cells, however in lesions Jak2vf comprised 50% of CD45+ cells, thus representing a clonal expansion within plaques. Through the aims proposed here, we will test the hypothesis that in a Jak2vf model of CH, increased inflammasome activation results in increased IL-1? secretion that potentiates M?? proliferation, pyroptosis, and atherogenesis. Aim 1 will test the hypothesis that in a hypercholesteremia-driven model of Jak2vf-CH, administration of IL-1? antibodies will result in decreased Jak2vf M?? proliferation, less M?? accumulation, and smaller lesions. Furthermore, we have previously reported Jak2vf mice have increased necrotic core formation, and recently we have discovered that deletion of Caspase1/11 normalizes necrotic core area in Jak2vf mice, suggesting increased pyroptosis mediated by downstream activation of GASDERMIN D. Therefore, Specific Aim 2 will examine the contribution of pyroptosis to necrotic core formation by breeding Gsdmd-/- mice with Jak2vf mice and examine Jak2vf-dependent signaling mechanism which may culminate in increased pyroptosis. Successful completion of the proposed studies will enhance our understanding of the mechanisms driving increased atherosclerosis in Jak2vf-mediated CH. Studies utilizing antibodies to IL-1?? may provide a foundation to consider using these therapies in humans.